[ Upstream commit 06f9a435b3aa12f4de6da91f11fdce8ce7b46205 ]
In subflow_syn_recv_sock() we currently skip options parsing
for OoO packet, given that such packets may not carry the relevant
MPC option.
If the peer generates an MPC+data TSO packet and some of the early
segments are lost or get reorder, we server will ignore the peer key,
causing transient, unexpected fallback to TCP.
The solution is always parsing the incoming MPTCP options, and
do the fallback only for in-order packets. This actually cleans
the existing code a bit.
Fixes: d22f4988ff ("mptcp: process MP_CAPABLE data option")
Reported-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
b198f77a36